1. Field of the Invention
The present invention relates to a working vehicle provided with a plurality of PTO shafts including an output end of a certain PTO shaft disposed oppositely to a main transaxle casing with respect to a center-Pivot transaxle casing.
2. Related Art
Conventionally, there is a well-known tractor having a center-pivot transaxle casing hung down from the lower surface of the tractor body through a center pin oriented longitudinally to the tractor, wherein the left and right ends of the axle casing can move vertically. The center pivoted transaxle casing usually supports steerable front wheels. Both of such supported left and right front wheels, even if the heights of ground surfaces to abut against the respective wheels are different, certainly grip the ground surfaces, thereby being easily steered. If the tractor is a 4WD type, the transaxle casing houses a differential gear which receives power from a main transmission for rear wheels.
There is also a well-known tractor with the center-pivot transaxle casing, which is provided with first and second PTO shafts; the first PTO shaft supported by a main transaxle casing usually for a rear-mount or mid-mount working machine, and an output end of the second PTO shaft disposed oppositely to the main transaxle casing with respect to the center-pivot transaxle casing.
The second PTO shaft has been driven by either an exclusive output shaft of an engine provided in addition to an output shaft of the engine for the main transmission in the main transaxle casing or power taken out from the main transmission. If the second PTO shaft is driven by the exclusive output shaft of the engine, the transmission system is extremely simplified and shortened because the engine is generally disposed in vicinity of the second PTO shaft or the center-pivot transaxle casing, however, the engine having the additional output shaft is expensive.
The second PTO shaft disposed in vicinity of the center-pivot transaxle casing must be prevented from interference with the center-pivot transaxle casing which tilts around the center pin during the traveling of the tractor. Conventionally, the second PTO shaft has been rotatably supported either through a tubal center pin pivoting the center-pivot transaxle casing or by a portion of the center-pivot transaxle casing lower than the center pin.
The second PTO shaft disposed through the tubal center pin is positionally fixed, thereby being fitted to be connected directly or through gears to the exclusive output shaft of the engine without a flexible transmission system. However, there arises the above-mentioned problem of expensiveness because of the unique engine.
If a transmission system is interposed between the second PTO shaft through the tubal center pin and the main transmission in the main transaxle casing, a center pin bracket usually formed of a vehicle frame is required to be further processed for supporting the second PTO shaft and parts for transmitting power to the second PTO shaft, thereby making the manufacture of the vehicle frame complicated and expensive. Also, a space for disposal of the transmission system between the main transmission and the second PTO shaft is limited between the main transaxle casing and the center pin, where an engine, a transmission system between the engine and the main transmission, a propeller shaft between the main transmission and the differential gear in the center-pivot transaxle casing and the like are concentrated. Thus, the transmission system between the main transmission and the second PTO shaft is difficult to be located and must bypass other parts, thereby being complicated, redundant and expensive. Furthermore, the center pin is generally higher than an input shaft of a working machine to be driven by the second PTO shaft. Thus, the transmission system between the second PTO shaft and the input shaft of the working machine is also complicated and redundant.
If the second PTO shaft is rotatably supported by a portion of the center-pivot transaxle casing lower than the center pin so as to be substantially as high as the input shaft of the working machine to be driven by the second PTO shaft, the transmission system between the second PTO shaft and the input shaft of the working machine is simplified and shortened.
However, it is still expensive to provide an additional exclusive output shaft for driving the second PTO shaft on whether an engine or the main transaxle casing. Particularly, if such an exclusive output shaft is provided on the main transaxle casing, the output shaft becomes adjacent to the first PTO shaft, thereby complicating the main transaxle casing. Furthermore, if a working machine driven by the first PTO shaft is disposed in the space between the main transaxle casing and the center-pivot transaxle casing, it should be considerable how to transmit power from the main transmission to the second PTO shaft.